They are that expensive, even when you try to find something at PC suppliers it won't be cheaper than at Amiga-dealers. I was hunting for a cheap solution but I was unable to find one. I even thought about soldering something myself, but getting loose parts and assembling that myself wasn't economically viable.
You could try cannibalising a dead PCMCIA card or something and the port of a dead laptop. Or accept defeat and buy one ;-).
